The present invention relates to a color image recording apparatus for producing a color image by selectively developing in different colors a plurality of latent images which are formed on a photoconductive element implemented by a belt and are each associated with respective one of the different colors, on a contact development basis.
Generally, an electronic color copier, color printer or similar color image recording apparatus has a plurality of developing units which individually store toners of different colors, e.g. yellow (Y), magenta (M), cyan (C) and black (BK). The developing units are selectively operated to develop latent images electrostatically formed on a photoconductive element by the toners of different colors. The resulting toner images are sequentially transferred to the same paper sheet one over another to produce a composite color image. A prerequisite with this kind of apparatus is that while a certain developing unit is operating in contact with the photoconductive element, the other developing units be spaced apart from the photoconductive element. Should the developing units not joining in the development under way be held in contact with the photoconductive element, the toners deposited on those developing units would disturb the latent image or the toner image already provided on the element. The above requirement may be met by adopting a system wherein each developing unit is shifted by a solenoid, spring or similar urging means, as proposed in the past. This kind of system, however, results in a complicated and expensive construction.
Recently, a color image recording apparatus of the type using a contact development system is drawing much attention. This kind of apparatus has a photoconductive element in the form of an endless belt. Specifically, among a plurality of developing units, one needed for development is caused into contact with the belt with the others being spaced apart from the belt so as to develop a latent image associated with a particular color and formed on the belt. The contact development system allows the development units to be moved into and out of contact with the belt by using the flexibility of the belt, thereby promoting the ease of selective development of latent images. A problem with the contact development system, however, is that when any of the developing units is urged against the belt, the belt is displaced at the contacting position and the amount such displacement varies in association with the developing unit. Hence, the timing for the belt to move away from an exposure station to a transfer station or the length of the belt between the exposure station and the transfer station depends on the developing unit. This prevents the toner images of different colors from being accurately brought into register with each other on the same paper sheet, resulting in the deviation of as well as banding.